Inspired by this contentious question.

The DMG indicates that to calculate a creature's save DC, the following formula should be used:

8 + Monster's Proficiency Bonus + Relevant Ability Score Modifier

Based on the criteria to calculate a creature's Save DCs, dragons' Frightful Presence save DC is based upon their Charisma modifier, which seems appropriate considering the manner in which the monster feature is supposed to work. Failing the save against this leaves the character Frightened for 1 minute or until they successfully save.

Suppose Bob the Fighter fails his save against an Ancient Blue Dragon's Frightful Presence (CR 23, Cha Mod +5, therefore save DC 20) and elects to continue fighting the dragon because he knows that with a +2 on his Wisdom save, he's never going to succeed and 1 minute is too long to be out of the fight. Subsequently, Melv the Wizard manages to connect with a Polymorph spell on the dragon and turns the dragon into a Frog (CR 0, Cha Mod -4, save DC 6).

Several questions from this:

  1. Does Bob need to continue making saves against Frightful Presence? Polymorph does not say it removes the monster's features and it is not like the Change Shape feature, which specifically specifies what features the dragon loses when using that ability.
  2. If Bob does need to continue making saves. What is the DC? Does it remain at 20 because that was the initial DC? Does it become 11 because the dragon's charisma modifier has been dropped by effectively 9 points, but the dragon retains the proficiency bonus? Or does the dragon also lose the proficiency bonus and the DC becomes 6?

What happens to Bob?

  • 3
    \$\begingroup\$ How is the second question not rehashing the question you've linked? \$\endgroup\$ Aug 25, 2017 at 3:42
  • \$\begingroup\$ @PurpleMonkey The original question related to a PC's spell save DC being subject to fluctuation. Monsters do not necessarily conform to the same rules as players and I'm curious if there is a difference in how this is handled. \$\endgroup\$ Aug 25, 2017 at 12:28

2 Answers 2


Bob is Frightened but there is almost no effect on him

The Frightened condition still persists, as there is nothing stopping or dispelling it in this case, but there is no effect because Frightened says:

(PHB 290)

  • A frightened creature has disadvantage on ability checks and attack rolls while the source of its fear is within line of sight.

  • The creature can't willingly move closer to the source of its fear.

Since the source of its fear was transformed into a frog, Bob does not suffer Disadvantage on checks and attacks, as Bob cannot currently see the Dragon.

As to whether or not Bob can move closer to the frog is contentious. Unlike the first bullet, the second effect does not require line of sight. I know I certainly wouldn't move closer to a frog that was, just a second ago, a Blue Dragon (What if the spell ends or it breaks free like one of those pokemon balls?!) I could see a DM ruling in either way, if the second effect persists or not, but I'd personally let the second bullet remain in effect, because it's funny.


Bob continues to make saving throws and the DC remains the same.

Firstly, frightful presence doesn't say anything about require the dragon to be in dragon form and polymorph says nothing about ending on-going effects. Much like polymorphing the caster of charm person wouldn't end the spell or charm effect on the charmee, polymorphing a dragon wouldn't automatically end it's frightful presence, because there's nothing to indicate that it would.

Secondly, the dragon's stat block gives a specific number for the saving throw. The DMG may say that the formula for determining a creature's save DC is:

8 + Monster's Proficiency Bonus + Relevant Ability Score Modifier

but that's not the way it's written in the stat block. The number that is given may even follow that formula but it's written as a static number, not something along the lines of:

"succeed on a DC equal to 8 + Monster's Proficiency Bonus + Relevant Ability Score Modifier".

Therefore it doesn't change due to the dragon being polymorphed.


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